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You are HERE >> Mathematics  > Grade 5

 
Divisibility Rules: No, it's not Cheating!
By Lisa Williams 
November 10, 2000

These rules are useful for kids from the time they start division, on. They keep me from using a calculator and most of the time, I can even work it in my head faster than the calulator because of these rules. I use them most when reducing awkward fractions. 
 
 

To Divide by ...
Cheat Codes
2 A number is divisible by 2 if it ends in 0 or an even number.

Example:   40 divided by 2 = 20 

           3974 divided by 2 = 1987
.

3 A number is divisible by 3 if the sum of the digits is divisible by 3.

Example: 321 add 3+2+1= 6 so 321 divided by 3 = 107

   2460 add 2+4+6+0= 12 so 2460 divided by 3 = 820



4 A number is divisible by 4 if the last 2 digits are both zeros or if they are divisible by 4.

Example:  300 divided by 4 = 75

               3548 divided by 4 = 887



5 A number is divisible by 5 if it ends in 0 or 5.

Example:  25 divided by 5 = 5

               400 divided by 5 = 80



6 A number is divisible by 6 if it is even and divisble by 3.

Example: 246 is even and 2+4+6 = 12 so 246 divided by 6 = 41



9 A number is divisible by 9 if the sum of the digits is divisible by 9.

Example: 81 add 8 + 1= 9 so 81 divided by 9 = 9

     972  add 9+7+2 = 18 so 972 divided by 9 = 18
 



10 A number is divisible by 10 if it ends in 0.

Example: 400 divided by 10 = 40

 

 

Submitted by: Copyright© Lisa Williams I'm a homeschooling mom of 3 elementary school age children. I run a clowning business from my home (Jingles the clown), am pianist for a local church, teach a Sunday School class, teach piano, tutor basic math see Math tutoring and algebra online and I enjoy making people smile. Send a note to Lisa
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